title: Blockade of telomerase function by nucleoside analogs.
abstract: Two types of spontaneously transformed cells appear in the culture of senescent mouse embryonic fibroblasts. The first type are cells with restricted proliferative potential (up to 30 population doublings); the other type are immortalized cells. Cells of the first type, unlike those of the second, have no telomerase activity and undergo two rounds of senescence. Spontaneous transformation of mouse embryonic fibroblasts in the presence of the reverse transcriptase inhibitors azidothymidine and carbovir led to the formation of telomerase-free clones. A fraction of these clones have the ability to overcome senescence via the acquisition of high telomerase activity. Cells with a very high level of telomerase activity become resistant to azidothymidine and carbovir. Azidothymidine-induced artificial senescence of rat myoblasts in culture resembles the senescence of fibroblasts, but the resulting cells acquire sharp morphological peculiarities. The blockade of telomerase function by azidothymidine in human U-937 and MeWo cells leads to the shortening of telomeres, but does not result in senescence. A hypothesis of the generation of the signal that induces senescence is proposed. This hypothesis suggests a change in DNA conformation during telomere shortening as a result of a change of loop structure of telomeric chromatin.
authors.affiliation: Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia. yegorov@genome.eimb.rssi.ru
authors.forename: Y E
authors.initials: YE
authors.lastname: Yegorov
authors.forename: D N
authors.initials: DN
authors.lastname: Chernov
authors.forename: S S
authors.initials: SS
authors.lastname: Akimov
authors.forename: A K
authors.initials: AK
authors.lastname: Akhmalisheva
authors.forename: Y B
authors.initials: YB
authors.lastname: Smirnova
authors.forename: D B
authors.initials: DB
authors.lastname: Shinkarev
authors.forename: I V
authors.initials: IV
authors.lastname: Semenova
authors.forename: I N
authors.initials: IN
authors.lastname: Yegorova
authors.forename: A V
authors.initials: AV
authors.lastname: Zelenin
mesh_terms: D000818:Animals; D002455:Cell Division; D002460:Cell Line; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D016922:Cellular Senescence; D002999:Clone Cells; D015224:Dideoxynucleosides / Q000494:pharmacology*; D005333:Fetus; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007700:Kinetics; D051379:Mice; D008808:Mice, Inbred CBA; D051381:Rats; D019098:Telomerase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015215:Zidovudine / Q000494:pharmacology*
chemical_list: D015224:Dideoxynucleosides; C057503:carbovir; D015215:Zidovudine; D019098:Telomerase